In factory automation and other commercial applications requiring control of motors and other electrical equipment, it is typical to mount electrical controls in a cabinet-styled enclosure. A door handle interlock mechanism is provided, so that when the door handle is operated to open the cabinet door and access the electrical control equipment, power is turned off. In particular, power to the other devices in the cabinet is supplied through a fused or non-fused disconnect switch. This switch may have multiple circuits or poles to handle polyphase voltages which may be supplied to the electrical equipment.
Once the cabinet has been opened, it may be desirable for service operations to again apply power to the devices in the cabinet. In the past, this was accomplished through certain types of methods for overriding the door interlock switch.
New standards have required that an on-off switch be provided in the interior of the cabinet for maintaining a locked-out “off” condition of the disconnect switch when the door of the enclosure is open. The standards also require that the switch be operable by qualified persons, independent of door position, and that in order to be switched to an “on” condition with the door open, the switch should require a deliberate action of the qualified person. The switch should also be capable of compatibility with various door interlock mechanisms available now and in the future.
Customers and applications require disconnect switches that can be provided in different configurations (e.g., with different numbers of poles, with front or side-operated switches, with rotary switch handles that are compliant with applicable standards, with or without lockout capability, and with or without network connectivity).
Customers prefer those disconnect switches which can be easily and quickly selected and assembled to satisfy their specifications. Such switches provide for high flexibility and a reduction in inventory costs. Network connectivity provides for faster diagnostics and servicing of the equipment at lower cost.